1. Field of the Invention
This invention relates generally to systems for receiving electromagnetic radiation, and more particularly, to an arrangement that is particularly suited to collect infrared electromagnetic radiation, particularly for determining the information content thereof.
2. Description of the Related Art
Conventional infrared detector arrangements suffer from multiple deficiencies, including insensitivity and small field of view. Oftentimes, the structure that is added to a photosensor to increase its field of view results in a decrease in sensitivity, particularly to light from a point source. Conversely, an increase in sensitivity is achieved at the expense of field of view. There is a need, therefore, for a detector arrangement that can achieve high sensitivity over a large aperture angle.
Sensitivity is achieved by effecting a more efficient collection of the ambient light, whereby a greater portion of the ambient light that impinges upon the infrared detector arrangement is delivered to the light-sensitive surface of a photodetector. In this regard, it is desired to reduce reflection of the ambient light.
Gradient-index (GRIN) lenses are known to achieve efficient collection of the ambient light in the infrared to visible range of optical frequencies. Such known arrangements, however, have a limited field of view and a limited effective light collection region. Thus, these limitations of GRIN lenses limit their utility per se as adequate data network nodes.
It is, therefore, an object ofthis invention to provide an inexpensive arrangement for receiving electromagnetic information signals propagated through air from a variety of directions.
It is another object of this invention to provide an inexpensive arrangement that efficiently receives and detects ambient light.
It is also an object of this invention to provide an apparatus that is useful as a data network node, particularly one that is operated in the infrared region of the electromagnetic spectrum.